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Egg-laying decisions by female insects should balance aspects related to immature survival and foraging profitability of emerging larvae. Using field-captured individuals, we characterized the egg distribution of Istocheta aldrichi (Diptera: Tachinidae) on the body of its adult host, the Japanese beetle Popillia japonica (Coleoptera: Scarabaeidae). We determined whether the pattern varies as a function of host sex and the number of eggs laid on a given host. Out of the 5667 eggs observed, 95.9% were located on the host pronotum. Furthermore, eggs on the pronotum were mostly positioned in the center of this sclerite and oriented perpendicular to the host body axis. The proportion of eggs placed on other parts of the host body increased with the number of eggs per host (superparasitism). Successful development of I. aldrichi into pupae was maximum for eggs laid on the host pronotum than for eggs laid on other parts of the host. Oviposition decisions in I. aldrichi are likely shaped by trade-offs between vulnerability to grooming by the host and foraging profitability of neonate larvae (i.e., their capacity to penetrate the host cuticle), but also by the mating and defensive behaviors of the Japanese beetle. [ABSTRACT FROM AUTHOR]

The Adzuki bean beetle (ABB), Callosobruchus chinensis infests and produces several successive generations in stored lentil (Lens culinaris); although all grains are not equally damaged by the insect. Thus, to answer the question why some of the grains are left undamaged, this study was conducted with the objective of determining if the observed difference either as damaged or undamaged in a stored grain is due to the difference in level of resistance to ABB. To achieve this objective a standard choice and no-choice tests were conducted using four lentil genotypes and 0 to 24 h old ABB. The two genotypes were derived from damaged lentil grains by ABB. Lentil genotypes and genotype by age interaction did not affect the number of eggs laid per female per day; the proportion of grains with eggs or holes; eggs per grain, holes per grain and mean developmental time. On the other hand, ABB age significantly affected all the parameters considered. The number of eggs laid per female per day increased from age two to age three and declined thereafter. All parameters but mean developmental time followed a similar patter as the number of eggs per female per day. On the contrary, mean developmental time increased continuously as the age of the ABB increased. This study confirmed that grains left undamaged in bulk stored grain are not resistant to Adzuki bean beetle. [ABSTRACT FROM AUTHOR]

Fish eggs collected in the West Mariana region of the western North Pacific (7°–18°N, 137°–144°E) were identified using mitochondrial 16S ribosomal RNA (16S rRNA) gene sequences, and their morphology and distribution were analyzed. Of the 5,321 eggs collected, 2,698 live eggs were morphologically divided into 108 types based on the character of shape, diameter, chorion, oil globule, pigmentation, yolk segmentation and perivitelline space. Excluding 20 types of formalin preserved eggs, partial sequences of 16S rRNA gene (1,019–1,190 base pairs) obtained for all remaining 88 types of ethanol preserved eggs were compared with sequences deposited in the DDBJ/EMBL/GenBank using Basic Local Alignment Search Tool. This resulted in 16 species being genetically identified and their morphological characters were observed including the first description of the eggs of three species, Ventrifossa garmani, Diodon hystrix, and Scopelogadus mizolepis. Distribution analysis showed that 52–100% eggs of eight species, Katsuwonus pelamis, D. hystrix, S. mizolepis, Thunnus spp., Xiphias gladius, Cepalopholis spp., Naso spp. and V. garmani were collected around seamounts of the West Mariana region, whereas the other eight species, Lampris guttatus, Oxyporhamphus micropterus, Ranzania laevis, Istiophorus platypterus, Exocoetidae spp., Lactoria diaphana, Tetrapturus angustirostris and Regalecus glesne showed no tendency to be concentrated around the seamounts and were widely distributed through the study area. These distributional patterns of eggs appeared to correspond well with the life histories of each species. The present study suggests that DNA species identification can provide a significant new tool for ecological studies on fish eggs. [ABSTRACT FROM AUTHOR]

Ophelimus maskelli (Ashmead) (Hymenoptera: Eulophidae), an invasive species in the Mediterranean area that occurs naturally on Eucalyptus camaldulensis at Wagga Wagga in New South Wales, was studied in Israel on the same host plant. The most distinctive characteristic of O. maskelli as compared with other congeners is the presence of only a single seta on the submarginal vein. O. maskelli shows a clear tendency to oviposit in developed, immature leaves, and it prefers to oviposit on an area of the leaf blade near the petiole. The female lays an average of 109 eggs when maintained on water alone. The egglaying distribution tended towards aggregation, and the same tendency has also been observed within and among trees. The wasp prefers to attack the lower canopy. The gall diameter ranged from 1.2 to 0.9 mm, and gall density from 11.5 to 36.0 galls cm−2, respectively. The typical color of the gall appeared as soon as third instar larva developed. Galls on shaded leaves remained green or greenish-yellow, whereas those that were exposed to the sun were reddish. O. maskelli produces three generations per year in Israel. High flight occurs among the spring generations, starting in early March. The wasps were attracted to green sticky plates much more than to the other tested colors. Heavy galling by O. maskelli results in premature shedding of the leaves, soon after the emergence of the wasps. Among the 84 eucalyptus species tested, the following 14 species were found to be suitable hosts: E. botryoides, E. bridgesiana, E. camaldulensis, E. cinerea, E. globulus, E. gunii, E. nicholii, E. pulverulenta, E. robusta, E. rudis, E. saligna, E. tereticornis and E. viminalis. This study focused on morphological and development characters that can clearly distinguish O. maskelli from Ophelimus eucalypti Gahan, and on examining the effect of crossing between eucalyptus species on the development possibilities of the wasps. Also considered were the effect of the food on adult survival, the competition between the eulophid gall maker Leptocybe invasa Fisher & LaSalle and O. maskelli, the heavy damage inflicted on eucalyptus, and the health problems and nuisance to people caused by the wasp near heavily infested trees during the mass emergence of adults. [ABSTRACT FROM AUTHOR]

Approximately three decades ago the question was first answered “whether parasitoids are able to assess the number or origin of eggs in a host” for a solitary parasitoid, Leptopilina heterotoma, by fitting theoretically derived distributions to empirical ones. We extend the set of different theoretically postulated distributions of eggs among hosts by combining searching modes and abilities in assessing host quality. In the models, parasitoids search either randomly (Poisson) (1) or by vibrotaxis (Negative Binomial) (2). Parasitoids are: (a) assumed to treat all hosts equally, (b) able to distinguish them in unparasitised and parasitised hosts only, (c) able to distinguish them by the number of eggs they contained, or (d) able to recognise their own eggs. Mathematically tractable combinations of searching mode (1 and 2) and abilities (a,b,c,d) result in seven different models ( M1 a, M1 b, M1 c, M1 d, M2 a, M2 b and M2 c). These models have been simulated for a varying number of searching parasitoids and various mean numbers of eggs per host. Each resulting distribution is fitted to all theoretical models. The model with the minimum Akaike's information criterion ( AIC) is chosen as the best fitting for each simulated distribution. We thus investigate the power of the AIC and for each distribution with a specified mean number of eggs per host we derive a frequency distribution for classification. Firstly, we discuss the simulations of models including random search ( M1 a, M1 b, M1 c and M1 d). For M1 a, M1 c and M1 d the simulated distributions are correctly classified in at least 70% of all cases. However, in a few cases model M1 b is only properly classified for intermediate mean values of eggs per host. The models including vibrotaxis as searching behaviour ( M2 a, M2 b and M2 c) cannot be distinguished from those with random search if the mean number of eggs per host is low. Among the models incorporating vibrotaxis the three abilities are detected analogously as in models with random search. Experiments with two species of solitary parasitoids ( L. heterotoma and Asobara tabida) are conducted. All theoretically postulated distributions are separately fitted to the resulting experimental egg distributions. The AIC criterion is used to choose the best fitting theoretical distribution. For both parasitoid species the frequency distribution of best fitting models for experimental data is compared to the classification of distributions generated by simulations. This leads to the conclusion that both L. heterotoma and A. tabida are able to distinguish between parasitised and unparasitised hosts. For L. heterotoma the results point to an ability to assess the number of eggs in a host, whereas A. tabida does not seem to have this ability. This difference suggests that an egg is more valuable for L. heterotoma than for A. tabida. [ABSTRACT FROM AUTHOR]

The spawning habits of Japanese surf smelt, Hypomesus pretiosus japonicus (Japanese name 'chika'), were studied from 1992 to 1995 at Akaiso Beach in Otsuchi Bay off the Pacific coast of northern Honshu. Investigations were conducted in relation to time, tidal rhythm, sand grain size on the spawning ground, and sex and age of spawners. Spawning occurred from late March to early May with its peak at the spring tide period during full moon in April. Before dark, fish gathered to school from 1-3 m depth, and 10-20 m off the shoreline of the spawning beach. Just before dark, they repeatedly approached the shoreline and stayed near the shoreline to spawn just after dark. In the spawning process, three intervals, i.e. aggregation, approach, and spawning, were recognized and these intervals are thought to be functionally connected. Mating occurred in a unit or group formed by one female and several males. During 1992-1995, except for 1994, spawning took place in a restricted region of the beach where backwash was stronger than other areas, and most sand grains were more than 1 mm in diameter and coarser than those of other areas. Although spawning was observed near the shoreline (34 to 120 cm tide level), most of the eggs were dispersed by backwash and each became attached to a few sand grains close to a step formed at 1-2 m depth off the spawning site. Spawners were composed mainly of age 0+ fish and some 1+ fish. Males usually outnumbered females on the spawning ground. Their spawning styles are discussed in relation to their ecology and habitat. [ABSTRACT FROM AUTHOR]